| If the variant interface says that the variant can
| go 'singular' or 'unspecified content' in *some* cases,
| The poor guy will have to handle it as a normal
| normal variant's interface. He would not care when
| and how the variant goes 'singular' or
| 'unspecified content'. If any of these can happen,
| he should handle it in his f() function.
| It is like f( char* p ). A good f() behaves well
| when p = NULL.

I disagree. A singular value is not like any other values. It is a
mistake to make people into believeing otherwise. People should be
encouraged to read docs and be careful about specs. Variant isn't the
kind of tools that the careless programmer is supposed to use.